Return to natural habitat in works for Agua Chinon

Irvine Ranch Conservancy Land Steward David Wilson hunts through brush in Agua Chinon Canyon in Irvine while searching for non-native invasive plant species during an ongoing habitat restoration project on Sunday morning. JEFF ANTENORE, FOR THE REGISTER

Species

$3.3 million: the approximate amount to be spent on habitat restoration

Species to be removed include:

Black mustard

Brome grasses

Tree tobacco

Species to be replanted include:

Mule fat scrub

Elderberry

Coastal sage scrub

When a raptor searches for a perch in certain stretches of Limestone Canyon north of Irvine carpeted by invasive grasses, it can't.

And the bobcat can't find the shelter it seeks.

The grasses and mustards have, through the years, crowded out the native shrubs, creating a monoculture not suited to many local animals.

But the Irvine Ranch Conservancy is spearheading a new five-year, nearly $3.3 million effort – funded by environmental mitigation dollars from O.C. Waste and Recycling and the Orange County Transportation Authority – to eliminate the invasive species and replant native shrubs across 30 acres near Agua Chinon Creek, an entry point to the popular Sinks hike.

"They have no natural predators, no way of keeping their population in check, so they basically run rampant across the landscape," said Lars Higdon, the conservancy's project manager for the Agua Chinon restoration.

To make sure the invasive plants are truly eliminated, the conservancy will first irrigate them to make them germinate – ensuring the stockpile of seeds in the soil is used up – then mow, pull and spray them, depending on the needs to the specific spot.

"We're not using just one technique to get rid of that weed one time," said Jutta Burger, the conservancy's director of science and stewardship, alleviating any worries that extermination efforts could breed a super weed. "They're going to have a really hard time getting wily on us."

Then, the replanted native plants will be irrigated to help them establish themselves.

The end result: a diverse, shrubby biome that resembles its original state. The restored area will help connect other areas of flourishing native habitat, offering wildlife more space to roam and more places to nest.

Scientists don't know the exact origin of the invasive species, but the black mustard, for instance, came from the Mediterranean area, either on the heals of settlers here, or the feet of imported animals. Some of the grasses might have been planted to provide feed for cattle herds, too.

Halfway around the world, the mustard has natural insect and animal predators. Here, those checks don't exist.

"You would never see masses, fields, of black mustard in Greece or Italy, the same kind of fields you see here," said Burger. "Their natural enemies don't occur here, and they're able to expand."

Black mustard in particular is perfectly suited to dominate Southern California's naturally diverse landscape – ecologically as diverse as the rainforest, but on a much smaller scale.

The broad, leafy leaves spread over the ground, blocking sunlight to other plants, while the thorny brush doesn't exactly taste good to most animals. The plants re-establish themselves quickly after flames char the landscape – an all too common occurrence in fire-prone SoCal. And, the mustard sends sterilizing chemicals into the soil.

California's native perennials are good eking out their existence year by year, but for them combating the aggressive weeds is much more difficult. Even years down the line, land managers will need to keep weeds in check to allow natives to flourish.

Irvine Ranch Conservancy Land Steward David Wilson hunts through brush in Agua Chinon Canyon in Irvine while searching for non-native invasive plant species during an ongoing habitat restoration project on Sunday morning. JEFF ANTENORE, FOR THE REGISTER
Irvine Ranch Conservancy Land Stewards David Wilson and Christina Van Oosten work in a riverbed in Irvine's Agua Chinon Canyon while removing non-native invasive plant species during a habitat restoration project on Sunday morning. JEFF ANTENORE, FOR THE REGISTER
Mark Sugars, a Land Steward for the Irvine Ranch Conservancy, cuts off seed-bearing branches from non-native Tree Tobacco during Sunday's Agua Chinon Canyon habitat restoration project. JEFF ANTENORE, FOR THE REGISTER
Christina Van Oosten, a Land Steward volunteer for the Irvine Ranch Conservancy, carries a bunch of non-native Tree Tobacco seedpods to be removed during Sunday's habitat restoration project in Irvine's Agua Chinon Canyon. JEFF ANTENORE, FOR THE REGISTER
Irvine Ranch Conservancy volunteer Land Stewards trek into Irvine's Agua Chinon Canyon looking for non-native plants to remove during a habitat restoration project on Sunday morning. JEFF ANTENORE, FOR THE REGISTER
David Wilson, a Land Steward for the Irvine Ranch Conservancy, uses a saw to cut the base of non-native Tree Tobacco during a habitat restoration project in Agua Chinon Canyon on Sunday morning. JEFF ANTENORE, FOR THE REGISTER
The natural sandstone cliffs at "The Sinks" are a popular destination for hikers and mountain bikers during the Irvine Ranch Conservancy's monthly Wilderness Access Days in Limestone and Agua Chinon Canyons. JEFF ANTENORE, FOR THE REGISTER
Mark Sugars, a Land Steward for the Irvine Ranch Conservancy, cuts non-native Tree Tobacco during Sunday's Agua Chinon Canyon habitat restoration project. JEFF ANTENORE, FOR THE REGISTER
David Wilson, a Land Steward for the Irvine Ranch Conservancy, uses a pickaxe to dig up the roots of non-native Tree Tobacco during a habitat restoration project in Agua Chinon Canyon on Sunday morning. JEFF ANTENORE, FOR THE REGISTER
David Wilson, a Land Steward for the Irvine Ranch Conservancy, drips herbicide onto the base of recently cut Tree Tobacco, to help ensure that the invasive non-native tree will not re-grow, during a habitat restoration project in Agua Chinon Canyon on Sunday. JEFF ANTENORE, FOR THE REGISTER
Irvine Ranch Conservancy Land Stewards David Wilson and Christina Van Oosten work in a riverbed in Irvine's Agua Chinon Canyon while removing non-native invasive plant species during a habitat restoration project on Sunday morning. JEFF ANTENORE, FOR THE REGISTER
David Wilson, a Land Steward for the Irvine Ranch Conservancy, pulls up the roots of non-native Tree Tobacco during a habitat restoration project in Agua Chinon Canyon on Sunday morning. JEFF ANTENORE, FOR THE REGISTER
David Wilson, a Land Steward for the Irvine Ranch Conservancy, marks locations on a map where he and his team removed non-native invasive Tree Tobacco, Castor Bean and Tamarisk plants during Sunday's habitat restoration project in Irvine's Agua Chinon Canyon. JEFF ANTENORE, FOR THE REGISTER
David Wilson, a Land Steward for the Irvine Ranch Conservancy, marks locations on a map where he and his team removed non-native invasive Tree Tobacco, Castor Bean and Tamarisk plants during Sunday's habitat restoration project in Irvine's Agua Chinon Canyon. JEFF ANTENORE, FOR THE REGISTER

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